In fabricating disk drives, such as energy assisted magnetic recording (EAMR) disk drives, it may be necessary to bond components together. For example, in conventional EAMR disk drives, a laser provides energy used to heat the media for magnetic recording. The laser typically takes the form of a laser diode. The laser diode may be desired to be aligned with a waveguide on the slider and bonded with the slider.
FIG. 1 depicts a conventional method 10 for bonding two substrates, such as a conventional laser diode (or substrate on which the laser diode resides) and a slider. FIGS. 2-3 depict a conventional EAMR head 50 during fabrication using the conventional method 10. FIG. 2 depicts a plan view of the substrates 60 and 70. Thus, two conventional substrates, a slider 60 and a laser diode 70 are shown. Each conventional substrate 60 and 70 includes conventional two-dimensional alignment marks 62 and 72, respectively. Although depicted as squares in FIG. 2, the alignment marks 62 and 72 may have a variety of shapes, including but not limited to interlocking shapes. Each conventional substrate 60 and 70 also includes conventional solder pads 64 and 74, respectively. The conventional substrates 60 and 70 are aligned, via step 12. Typically this is accomplished by aligning the alignment marks 62 on one substrate 60 with the alignment marks 72 on the other substrate 72. FIG. 3 depicts the conventional substrates 60 and 70 after step 12. Thus, the alignment marks 62 and 72 and solder pads 64 and 74 are aligned. The alignment marks 62 and 72 are two-dimensional alignment marks viewable from the planar surfaces of the substrates 60 and 70 on which the solder pads 64 and 74 reside and which are being aligned. Thus, the alignment marks 62 and 72 are depicted as dashed lines in FIG. 3. Once alignment has been achieved, the substrates 60 and 70 are heated to reflow the solder 64 and 74. Mechanical and electrical connection is made between the substrates 60 and 70 by pads 64′/74′, which have been reflowed together.
Although the conventional method 10 may function, the method 10 may be problematic for certain technologies. For example, an edge emitting laser may be desired to be used. An edge emitting layers has an emission exit for laser light on the edge of the substrate. The edge emitting layers may be aligned as shown in FIGS. 1-3. However, in such a case, optical components (not shown) may be required to redirect light from the edge of the laser diode 70 to a waveguide on the substrate/slider 60. If the emission edge is to be oriented closest to the slider 60, then the conventional substrate 70 would be placed such that an edge is closest to the substrate/slider 60. Thus, the conventional substrate/laser diode 70 would be oriented perpendicular to what is shown in FIGS. 2-3. In such a case, however, alignment using two-dimensional alignment marks 62 and 72 may be difficult to accomplish. Fabrication of conventional two-dimensional alignment marks on the edge of the substrate 70 may be challenging. Conversely, alignment without such marks may be extremely difficult to accomplish.
Accordingly, what is needed are improved methods and systems for aligning substrates, for example in alignment of substrates used in EAMR disk drives.